The present invention relates to an asynchronous machine by way of example in the form of an electrical asynchronous motor or a generator.
Electrical machines are being developed in order in the future by way of example to render it possible to drive electric vehicles or hybrid vehicles in an electrical manner or rather to be able to recoup kinetic energy of the vehicle into electrical energy. The electrical machine can function either as a motor or as a generator.
Various electrical machines are currently being further developed in particular for use in vehicles. In particular, efforts are being undertaken to optimize asynchronous machines for use in vehicles. Above all, for future road-going vehicles, the asynchronous machine for this purpose on the one hand should be as small and light as possible and on the other hand should be highly efficient whilst outputting as much power as possible and providing the maximum torque.
Asynchronous machines comprise a stator and a rotor as essential components. Similar to other electrical machines, one or multiple windings is/are housed in the stator with the aid of which it is possible to generate a rotating magnetic field in the stator. However, in contrast to many other types of electrical machines, magnets in the form of permanent magnets or electromagnets that are supplied with energy from the exterior are not provided on the rotor that can rotate relative to the stator. In lieu of said magnets, the rotor comprises a generally short-circuited conductor that is in part also described as a passive armature. The rotating magnetic field that is generated by the stator rotates with a so-called synchronous rotational speed that corresponds to the quotient f1/p from the fundamental frequency f1 of the system that is supplying energy and the pole pair number p. As soon as the mechanical rotational speed of the rotor differs from the synchronous rotational speed, the rotor experiences a change in the magnetic flux. As a consequence, currents are induced in the short-circuited rotor conductors. A torque occurring between the stator and the rotor is produced by means of an interaction between the rotating magnetic field of the stator and the rotor currents.
One example of an asynchronous machine that is also in part described as an induction motor is described in EP 2 202 781 A2.